The present invention relates to a medical instrument system for removing foreign objects from a tubular body, more particular, to an instrument system used for extraction of stones or calculi that may be obstructing the ureter.
The ureter is a narrow mucous-lined tubular canal connecting the kidney and bladder for the passage of urine. Stones are formed in the kidney and may pass down through the ureter to the bladder, then are usually voided naturally through the urethra. These calculi occasionally become trapped in the ureter because of irregular barbed surfaces of the calculi or for other reasons such as normal and pathological narrowing of the ureter. As a result, they remain in the ureter and may obstruct the passage of urine. The resultant accumulating back pressure of urine may then cause impaired function of the kidney, infection, or intense pain and discomfort to the patient. One acceptable method of removing the obstruction is to endoscopically remove the stone by capturing it with an instrument inserted through the ureter. One prior technique of this method involved using a cystoscope introduced into the bladder and passing up the ureter toward the stone, a non-sheathed umbrella-like instrument, which is called a stone basket. This basket would be passed beyond the stone and once upstream from the stone, the basket would be pulled downstream in order to capture the stone in its webbing and then extract it. An example of such a stone basket is illustrated in the 1948 BARD Catalogue, No. 344-Johnson Stone Basket.
Another prior art device is a sheath basket in which the metal wire webbing basket is positioned within a hollow tubular catheter therefore sheathing the otherwise exposed wires. In this manner, the operator passes a sheathed stone basket up the ureter beyond the stone. At that point, the operator would push the stone basket up and out the distal end of the catheter, opening the basket, and then manipulating the basket down-stream in order to try to capture the stone and extract it in the basket.
As with both the sheath and non-sheathed baskets, there is a great danger to the ureter in passing these instruments. They may cause trauma and damage to the ureter especially if forced through the constricted or swollen ureteral area around the stone. The danger of trauma to the ureter by a ureteral instrument device cannot be overemphasized, if the ureteral device injures the ureter, the device itself may become imbedded and trapped in the ureter or may tear the ureter while trying to extricate it. In that event, full scale surgery with its inherent morbidity and mortality is then required to repair the ureter and/or to remove the device and to remove the stone.
These sheathed and non-sheathed stone baskets of the prior arts are relatively large in diameter, although they are somewhat smaller than the inside diameter of the ureter. More recently, in the instrumentation of the ureter there has come to be a guide wire, which is used to traverse the ureter. This is much smaller than the stone baskets and is much safer. A most recent prior art device is now being used which is the Carson Stone Basket. This was described in an article printed in the October 1984 edition of "Urology". The Carson Basket slides over the previously inserted guide wire which has already passed the stone. It is obvious that if the guide wire is in place it is much easier and safer to pass the stone basket beyond the calculus. The only problem with the Carson device is it still has the exposed wire webbing which may be a hazard to the ureter in its passage.
As a result, there still remains, with the use of all the prior art devices, a high possibility of accidental trauma caused by the stone basket's probing the narrow passageway between the stone and the ureter. The object of the present invention is to provide a method and system of removing the ureteral stones by minimizing the risk of ureteral trauma.
With the advent of the percutaneous approach to the kidney, ureteral calculi have now been approached antigrade from the kidney down the ureter. Because of the need to retain a safety guide wire in place during the procedure, in the present invention a second guide wire would be passed down the ureter and beyond the stone. Then a sheath would be percutaneously passed over the second guide wire down the ureter until it was below the calculus. The guide wire would then be removed and the stone basket would be loaded antigrade into the sheath and passed down the ureter and beyond the stone. The stone basket would be opened beyond the stone and brought back up the ureter until it engaged the stone and then extracted it.
Another recent development is the use of a ureteroscope which gives direct visualization within the ureter, permitting one to directly observe the calculus while extracting it. The device of the present invention can be used in combination with the ureteroscope so that the extraction can be performed under direct visualization. This enables extraction of calculus with substantially less risk and trauma. The instrument described herein is designed to take advantage of the ability to pass guide wires down antigrade from the kidney percutaneously into the ureter.